The Ministry of Defence launched a fresh inquiry into racism in the army last night after the Guardian uncovered a series of extreme and offensive comments on the social networking site Facebook.

The racist remarks were posted by people claiming to be serving soldiers. One writer's espoused political idea was to "kill the paks", while another listed having an interest in "ethnic cleansing" and enjoying "SS marching music".

Many of the remarks referred to "Pakis" and "ragheads", and on one discussion thread someone from the West Midlands claimed there was deep-seated hatred of immigrants in the UK among many troops, who were, the writer thought, sick of seeing people burn flags and preaching hate on British streets.

The comments follow the publication of a video of Prince Harry last week in which the third in line to the throne described another soldier as a "Paki".

The prince's remarks drew widespread criticism from equality campaigners, and the Equality and Human Rights Commission demanded an inquiry. A spokeswoman said the watchdog would press the armed forces to dismantle its racist "barrack-room culture".

The Guardian has given the commission a dossier containing the comments from the social networking site.

Many of those who wrote on this Facebook site expressed support for the far-right British National party. One gave an army number and base before asking others on the message board: "Anyone fancy a spot of Paki bashing?"

Others joined a thread called "I'm a soldier why should i fight for stealing immigrant scum".

Equality campaigners said that the level of racism and extremism expressed underlined the need for the army to take immediate action.

"These comments show quite clearly that racism still exists within the army," said Mohammed Shafiq, chief executive of the Ramadan Foundation, a Muslim youth group. "There has undoubtedly been a huge change in attitude among senior ranks and ministers but this shows that has simply not trickled down to the rank and file ... If the army truly wants to start recruiting more people from an ethnic minority background this has got to be addressed as a matter of urgency."

The MoD said it would investigate the remarks, insisting it was committed to "a working environment which is free from harassment, intimidation and unlawful discrimination".

A senior military source told the Guardian that anyone found to "hold the views" expressed by those Facebook correspondents would be "hunted down and dealt with most severely" if it was clear they had not met the army's "required high standards of behaviour". The source added: "If these people are soldiers and do genuinely have these opinions I don't think there is any genuine soldier or officer who would want them in their army. But I know from my experience they represent a tiny, tiny percentage ... in the UK's armed forces."

The MoD claimed progress in tackling racism, saying the percentage of forces from an ethnic minority background rose from 5.9% last year to 6.3%, though the target was 8%. It aimed to employ forces staff "from all of the UK's diverse communities so we reflect the society we serve".